1. Field of the Invention
This invention relates in general to surveillance radar systems which are protected from anti-radar missiles by using a transmitter which radiates a continuous wave signal of constant mean power upon which is impressed coding such that range resolution of the target echo signals can be accomplished by receivers using decoding.
2. Description of the Prior Art
Reconnaissance radars operate with strongly directional beam antennas which are jointly used for transmitting and receiving and operate with short pulses of high peak power.
Anti-radar missiles ARM are in the process of being developed and utilized for the destruction of radar apparatus and such missiles have search heads which utilize the radio frequency radiation of the radar apparatus to locate and guide the missile to the radar apparatus for its destruction.
The periodic regular rotation of the antenna allows the attacking missile to be periodically radiated by the major lobe of the antenna of the radar and the received radar energy is received in a time pulse which is sufficient for steering guidance of the missile. For this reason, the defense of the radar installation by using fraudulent or illusory transmitters is ineffective.
One attempt to prevent the homing in of anti-radiation missiles ARM has been to use a continuous wave signal of equal mean power instead of short pulses of high power with the continuous wave signal being modulated with a code for a range resolution.